String Replacement Ruby regex

Question

I need to replace a string of characters with a sequence; I am using the gsub method

Say,

name = "Tom"

and this appears in a text as $(name) i need to replace $(name) with Tom.

Now, it is replacing only name with Tom and not $(name) with Tom. Can you tell me how the gsub will be like.

Show your gsub, perhaps? Also, why do you replace name and not $(name)? — Sergio Tulentsev
– Sergio Tulentsev, Commented Jul 7, 2015 at 19:00
The my_hash contains the name =>Tom correspondence. The gsub is as line.gsub($2 , my_hash). I get $2 from the regex that gives me "name" — Sakshi Malhotra
– Sakshi Malhotra, Commented Jul 7, 2015 at 19:02
@SergioTulentsev: I need to replace $(name). now the output I am getting is $(Tom), not only Tom — Sakshi Malhotra
– Sakshi Malhotra, Commented Jul 7, 2015 at 19:06

tadman · Accepted Answer · 2015-07-07 19:06:09Z

3

Don't forget to properly escape things:

string = "My name is $(name)"

string.gsub(/\$\(name\)/, "Tom")
# => My name is Tom

Of course you can easily make this more generic:

substs = {
  name: "Tom"
}

string.gsub(/\$\((\w+)\)/) do |s|
  substs[$1.to_sym]
end

answered Jul 7, 2015 at 19:06

tadman

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2 Comments

Sakshi Malhotra Over a year ago

Hi, Can you show me an implementation of your second code. I am very new to ruby and would like to know how to use it

tadman Over a year ago

You mean an explanation? That's a regular expression that captures word-like values (\w+) and uses that to look-up in a Hash what to replace it with. That can be a lot to take in at first, but take it bit by bit and you'll come to understand it better. Techniques like this can do a lot of work with very little code. If you've got a good Ruby reference, that helps considerably.

michael_wu · Accepted Answer · 2015-07-07 19:02:31Z

2

str.gsub('$(name)', 'Tom')

or, with a regexp

str.gsub(/\$\(name\)/, 'Tom')

answered Jul 7, 2015 at 19:02

michael_wu

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Comments

steenslag · Accepted Answer · 2015-07-07 19:57:23Z

2

str = "and this appears in a text as $(name) i need to replace $(name) with Tom."
str.tr!("$()","%{}") # use ruby's sprintf syntax %{name}
some_name = "Tom"

p str % {name: some_name}
# => "and this appears in a text as Tom i need to replace Tom with Tom."

answered Jul 7, 2015 at 19:57

steenslag

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2 Comments

tadman Over a year ago

That is a clever approach, though hopefully no %{...} content was present in the original.

Sakshi Malhotra Over a year ago

thanks, but i don't think i will be able to use this as i am not aware in the data i will be parsing if i may encounter a %{...}

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